The present invention relates to materials handling apparatus and, more particularly, to a conveyor of the walking beam or jogging type wherein a work piece is moved step wise along a conveying path. In a particular embodiment, the present invention is directed to a weighing apparatus employing a walking beam conveyor mechanism.
It is common in many industrial applications to employ conveyors both of the continuous and walking beam type to move work pieces, e.g. containers, drums, or the like, along a conveying path along which are spaced work stations at which various operations may be performed on the work piece. For example, in the case of containers or drums which are to be filled with a material, the container can be moved through various stations such as filling/weighing, capping, labelling, etc.
In the filling of containers or drums with either liquid or solid material, it is desirable to perform the filling automatically so as to speed up the operation. In such automated filling systems, it is generally necessary, either manually or with a container alignment apparatus, to align the container on the conveyor system such that the fill opening in the container or drum will be properly aligned beneath a fill valve, spout, filling spear or similar device used to feed the material into the container through the fill opening. In the case of continuous conveyors such as for example roller type conveyors and, as is well known in the art, as a container moves along the rollers it changes orientation because of varying frictional forces encountered as the container moves across the rollers, irregularities in the bottom of the container and other such factors. Thus, assuming that the container was properly oriented at an alignment station on the conveyor path such that the fill valve and the fill opening would be in register when the container moved to the fill station, it will be appreciated that because the container will lose orientation for reasons discussed above, when the container arrives at the fill station the fill valve and the fill opening are frequently not in register. The problem is particularly acute in cases where the fill valve is only slightly smaller than the fill opening since only a small change in the orientation of the container in moving from the alignment station to the fill station will result in the fill valve and the fill opening being out of register. When this occurs, it is necessary for an operator to manually adjust the position of the drum relative to the fill valve so as to place the fill valve and the fill opening in register. Not only is this time consuming, but in the case of hazardous materials such as corrosive or toxic chemicals, it can be a safety hazard as well. Accordingly, it is common practice, when continuous type conveyor systems are used, to align the container at the fill station to ensure proper register between the fill valve and the fill opening. However, this solution is not totally satisfactory since two, relatively time consuming functions must be accomplished at the same station and cannot be accomplished simultaneously. It is clearly desirable to separate the alignment and fill steps thereby eliminating from the time cycle the time of alignment. In this regard it is to be noted that, generally speaking, the fill step is of the longest duration meaning that other operations can be performed on the container during the fill step.
Over and above the problems associated in continuous type conveyor systems, with alignment and filling of a container, there is the added problem that once the container has been filled, it generally moves to a subsequent station(s) for capping of the fill opening. During its movement from the fill station to the capping station(s), and for reasons outlined above, the container will usually change orientation such that if an automatic capping apparatus is used which requires that the fill opening be in a given position, it is necessary, once again, to either manually or automatically align the container at the capping station to bring the capping apparatus and the fill opening into proper orientation or register with one another. It will be appreciated that the capping process may include several work stations such as cap placement, cap securing the cap sealing all of which can generally not be accomplished at the same work station meaning that at each station an alignment problem may be presented. In addition to the above difficulties associated with continuous type conveyors, a problem not to be overlokked, particularly when the material with which the container is to be filled is a liquid material which is of a hazardous nature, is the fact that as the drum or container moves along the conveyor prior to being capped, and whether the continuous conveyor is of the roller type or belt type there is a tendency for the liquid material to "slosh" back and forth either because of intermittent or jerky movement of the conveyor, irregularities in the bottom of the container in contact with the conveyor surface or other such factors. Indeed, the material can slosh out of the fill hole and onto nearby workers posing an extremely serious health hazard. To overcome this problem, it is common at a first fill station to fill the container to a first, predetermined weight and then to "top out" the container with remaining material to the desired fill weight at the capping station. This again is an extremely time consuming operation and requires complicated apparatus.
It is known to use walking beam conveyors for moving containers stepwise through a series of operations or work stations. In walking beam conveyor systems, once the container has been positioned on the moving portion of the walking beam assembly, it continues to move through the conveying cycle stepwise without losing its original orientation so that the container is in registry with each work operation to be performed along the conveying path. A typical walking beam conveyor for use in handling containers is disclosed in U.S. Pat. No. 4,102,450. U.S. Pat. Nos. 3,666,086 and 4,148,400 also disclose walking beam or similar conveyor systems for moving work pieces.
One problem associated with the use of walking beam conveyors is that because of their intrinsic motion, problems are encountered in continuous and automatic feeding of work pieces, e.g. containers, on to the moving support portion of the walking beam conveyor. Walking beam conveyors have a movement, depending upon their particular construction, which follows an approximately rectangular path, or a distorted rectangular path somewhere between a rectangle and a circle. Thus, unlike the continuous type conveyor which forms a single support surface lying and moving generally in a single plane, walking beam conveyors have two support surfaces which are, intrinsically, not always in the same plane.
Weighing systems used with continuous, roller type conveyor systems are complicated and create accuracy problems in weighing. For one, in such weighing systems, it is necessary to "break" the roller conveyor and provide a small, individual section of rollers upon which the drum or container rests at the fill station, the individual section of rollers resting on a scale beneath the fill station. In order to move the drum off of the scale when the fill cycle is completed, the broken section of rollers must also be motorized. Since the scale thus must support not only the drum or container but the roller section as well as the motor, it must have a larger capacity and is, therefore, intrinsically less accurate. Additionally, cleanliness at the fill station becomes a problem. Since the scale is beneath the roller conveyor, any spills that occur can only be effectively cleaned up by moving the scale and its associated roller section from beneath the fill station. This is time consuming and, in the case of filling containers with hazardous materials such as corrosive or toxic chemicals, can pose a health threat to the workers.